Dietary Patterns of 479 Indonesian Adults and Their Associations with Sodium and Potassium Intakes Estimated by Two 24-h Urine Collections

The excess sodium (Na) intake and insufficient potassium (K) intake are frequently observed all over the world, including Indonesia. This study explored the dietary patterns of Indonesian people and evaluated their associations with Na and K intakes. Na and K intakes were assessed by repeated 24-h urine collection. The dietary patterns of the previous month were extracted by factor analysis using the Indonesian Food Frequency Questionnaire. The participants were community-dwelling Indonesian men and women (n = 479) aged 20 years and over. We identified four dietary patterns in each sex. After controlling for confounding factors, the high quantile of ‘Noodle, oil, and salty sea products’ pattern was associated with the high Na intake in both men and women (p = 0.02 and <0.001, respectively). The ‘Meat, vegetable, oil, and fruit’ pattern statistically significantly contributed to the high K intake in men (p = 0.04), but not in women (p = 0.26). The ‘Vegetable, non-oil, and milk’ pattern in men and ‘Meat, vegetable, and fruit’ pattern in women were associated with low Na:K ratios (p = 0.03 and 0.01, respectively). Neither ‘bread’ nor ‘fish’ appeared as a major determinant of any dietary patterns in this population. The ‘Noodle, oil, and salty sea products’ pattern should be avoided to reduce sodium intake.

Potassium Intake-(Un)Expected Non-Predictor of Higher Serum Potassium Levels in Hemodialysis DASH Diet Consumers

As high serum potassium levels can lead to adverse outcomes in hemodialysis (HD) patients, dietary potassium is frequently restricted in these patients. However, recent studies have questioned whether dietary potassium really affects serum potassium levels. The dietary approaches to stop hypertension (DASH) diet is considered a healthy dietary pattern that has been related to lower risk of developing end-stage kidney disease. The aim of this study was to analyze the association between a dietary pattern with high content of potassium-rich foods and serum potassium levels in HD patients. This was an observational, cross-sectional, multicenter study with 582 HD patients from 37 dialysis centers. Clinical and biochemical data were registered. Dietary intake was obtained using the Food Frequency Questionnaire. Adherence to the DASH dietary pattern was obtained from Fung’s DASH index. All statistical tests were performed using SPSS 26.0 software. A p-value lower than 0.05 was considered statistically significant. Patients’ mean age was 67.8 ± 17.7 years and median HD vintage was 65 (43−104) months. Mean serum potassium was 5.3 ± 0.67 mEq/L, dietary potassium intake was 2465 ± 1005 mg/day and mean Fung´s Dash Index was 23.9 ± 3.9. Compared to the lower adherence to the DASH dietary pattern, patients with a higher adherence to the DASH dietary pattern were older (p < 0.001); presented lower serum potassium (p = 0.021), serum sodium (p = 0.028), total fat intake (p = 0.001) and sodium intake (p < 0.001); and had higher carbohydrate intake (p < 0.001), fiber intake (p < 0.001), potassium intake (p < 0.001), phosphorus intake (p < 0.001) and body mass index (p = 0.002). A higher adherence to this dietary pattern was a predictor of lower serum potassium levels (p = 0.004), even in the adjusted model (p = 0.016). Following the DASH dietary pattern, which is rich in potassium, is not associated with increased serum potassium levels in HD patients. Furthermore, a higher adherence to the DASH dietary pattern predicts lower serum potassium levels. Therefore, generalized dietary potassium restrictions may not be adequate, at least for those with a DASH diet plan.

Associations of sodium and potassium intake with chronic kidney disease in a prospective cohort study: findings from the Hispanic Community Health Study/Study of Latinos, 2008-2017

BACKGROUND

According to dietary recommendations, reduction of sodium intake has potential to reduce Chronic Kidney Disease (CKD) risk; however the role of dietary potassium and the sodium -to- potassium ratio in the development of CKD is unclear.

METHODS

We studied 9778 participants of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) from four US urban communities. Participants were aged 18-74 yrs., free from CKD at baseline in 2008-2011 and re-examined between 2014 and - 2017. Dietary intake of sodium, potassium and the ratio of dietary sodium -to- potassium were measured from two baseline 24-h dietary recalls. Incident CKD was defined as: 1) estimated glomerular filtration rate (eGFR) decline of 1 unit per year and eGFR < 60 ml/min/1.73m2 or 2) albumin to creatinine ratio ≥ 30 mg/g at the follow-up visit. We used multivariable survey weighted Poisson regression to estimate adjusted incident rates of incident CKD.

RESULTS

At baseline, mean age was 41 years. Average follow up time was 6.2 years. From fully adjusted Poisson regression analyses, self-reported sodium intake was not associated with incident CKD. However, for each 500 mg decrement in potassium intake, there was an 11% increase risk of incident CKD (IRR = 1.11, 95% CI = 1.00, 1.24). Additionally, every 1 M ratio increment of sodium -to -potassium ratio was associated with a 21% increased risk of incident CKD (IRR = 1.21, 95% CI = 1.02, 1.45), p < 0.05).

CONCLUSIONS

We conclude that diets low in potassium and high in sodium are associated with increased risk of developing chronic kidney disease among healthy US Hispanic/Latino adults.

Dietary Potassium Intake and Mortality in a Prospective Hemodialysis Cohort

OBJECTIVES

Among hemodialysis patients, clinical practice guidelines recommend dietary potassium restriction given concerns about potential hyperkalemia leading to malignant arrhythmias and mortality. However, there are sparse data informing recommendations for dietary potassium intake in this population. We thus sought to examine the relationship between dietary potassium intake and death risk in a prospective cohort of hemodialysis patients.

DESIGN AND METHODS

Among 415 hemodialysis patients from the prospective "Malnutrition, Diet, and Racial Disparities in Chronic Kidney Disease" cohort recruited across 16 outpatient dialysis clinics, information regarding dietary potassium intake was obtained using Food Frequency Questionnaires administered over October 2011 to March 2015. We first examined associations of baseline dietary potassium intake categorized as tertiles with mortality risk using Cox regression. We then examined clinical characteristics associated with low dietary potassium intake (defined as the lowest tertile) using logistic regression.

RESULTS

In expanded case-mix Cox analyses, patients whose dietary potassium intake was in the lowest tertile had higher mortality (ref: highest tertile) (adjusted hazard ratio 1.74, 95% confidence interval 1.14-2.66). These associations had even greater magnitude of risk following adjustment for laboratory and nutritional covariates (adjusted hazard ratio 2.65, 95% confidence interval 1.40-5.04). In expanded case-mix restricted cubic spline analyses, there was a monotonic increase in mortality risk with incrementally lower dietary potassium intake. In expanded case-mix logistic regression models, female sex; higher serum bicarbonate; and lower dietary energy, protein, and fiber intake were associated with low dietary potassium intake.

CONCLUSIONS

In a prospective cohort of hemodialysis patients, lower dietary potassium intake was associated with higher mortality risk. These findings suggest that excessive dietary potassium restriction may be deleterious in hemodialysis patients, and further studies are needed to determine the optimal dietary potassium intake in this population.

The dietary management of potassium in children with CKD stages 2-5 and on dialysis-clinical practice recommendations from the Pediatric Renal Nutrition Taskforce

Dyskalemias are often seen in children with chronic kidney disease (CKD). While hyperkalemia is common, with an increasing prevalence as glomerular filtration rate declines, hypokalemia may also occur, particularly in children with renal tubular disorders and those on intensive dialysis regimens. Dietary assessment and adjustment of potassium intake is critically important in children with CKD as hyperkalemia can be life-threatening. Manipulation of dietary potassium can be challenging as it may affect the intake of other nutrients and reduce palatability. The Pediatric Renal Nutrition Taskforce (PRNT), an international team of pediatric renal dietitians and pediatric nephrologists, has developed clinical practice recommendations (CPRs) for the dietary management of potassium in children with CKD stages 2-5 and on dialysis (CKD2-5D). We describe the assessment of dietary potassium intake, requirements for potassium in healthy children, and the dietary management of hypo- and hyperkalemia in children with CKD2-5D. Common potassium containing foods are described and approaches to adjusting potassium intake that can be incorporated into everyday practice discussed. Given the poor quality of evidence available, a Delphi survey was conducted to seek consensus from international experts. Statements with a low grade or those that are opinion-based must be carefully considered and adapted to individual patient needs, based on the clinical judgment of the treating physician and dietitian. These CPRs will be regularly audited and updated by the PRNT.

Sodium and Potassium Intake and Cardiovascular Disease in Older People: A Systematic Review

This review aims to examine the relationship of sodium and potassium intake and cardiovascular disease (CVD) among older people. Methods: We performed a literature search using PubMed and Web of Science (January 2015 to July 2020) without language restriction. Observational and experimental studies that reported the relationship between sodium, potassium, or sodium-to-potassium ratio with CVD among older adults aged higher than 60 years were included. The authors independently screened all identified studies, extracted information, and assessed the quality of included studies. Risk of bias was assessed using the Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS) for observational studies and the revised Cochrane risk-of-bias tool (RoB 2 tool) for randomized trials. Results: We included 12 studies (6 prospective cohort studies, 5 cross-sectional studies, and 1 experimental study). Five of the studies reported on sodium-to-potassium ratio (n = 5), and the others on potassium and/or sodium intake. Cardiovascular events (e.g., stroke and heart failure) were the most reported outcome (n = 9). Of the 12 studies included, five observational studies had low bias risk and the randomized controlled trial was judged as uncertain risk of bias. We found inconsistent results for the effect of the reduction of sodium intake in this population for lower risk of CVD. We found that both the increase of potassium intake and the decrease of sodium-to-potassium ratio were associated with lower risk of hypertension and CVD, particularly stroke. Conclusion: The present review suggests that both higher potassium and lower sodium-to-potassium ratio are associated with lower risk of CVD.

How to Manage Hypertension in People With Diabetes

Hypertension is a common condition that is often seen in patients with diabetes. Both diseases increase the risk of morbidity and mortality from CV events and kidney disease progression. Factors that influence blood pressure (BP) control in diabetes include the persons' genetic background for hypertension and kidney disease, level of obesity and insulin resistance, the magnitude of preexisting kidney disease, and lifestyle factors, such as level of sodium and potassium intake, sleep quality and exercise effort all of which can affect levels of sympathetic nerve activity and contribute to increased BP variability. Lifestyle intervention is a key component to the effective management of diabetes and hypertension and can markedly reduce event rates of both heart and kidney outcomes. The approach to pharmacologic treatment of BP in diabetes is crucial since certain classes of agents for both BP and diabetes confer significant benefits to reduce cardiorenal outcomes.

Dietary and lifestyle factors for primary prevention of nephrolithiasis: a systematic review and meta-analysis

BACKGROUND

Dietary and lifestyle factors may play an important role in the increasing prevalence of nephrolithiasis. We aimed to review and quantify the associations between lifestyle factors and incident nephrolithiasis and suggest lifestyle changes for the primary prevention of nephrolithiasis.

METHODS

PubMed, EMBASE, and Cochrane Library were searched up to May 2019, for observational studies and randomized controlled trials (RCTs) that assessed modifiable lifestyle factors and risk of nephrolithiasis in adults. Pooled relative risks (RRs) and 95% confidence intervals (CIs) were computed using a random effects model. The I² statistic was employed to evaluate heterogeneity. Subgroup analysis, sensitivity analysis and meta-regression were also conducted whenever possible.

RESULTS

Fifty relevant articles with 1,322,133 participants and 21,030 cases in total were identified. Prominent risk factors for incident stones were body mass index (1.39,1.27-1.52), dietary sodium (1.38, 1.21-1.56), fructose, meat, animal protein, and soda. In contrast, protective factors included fluid intake (0.55, 0.51-0.60), a Dietary Approaches to Stop Hypertension (DASH) style diet (0.69, 0.64-0.75), alcohol (0.69, 0.56-0.85), water, coffee, tea, vegetables, fruits, dietary fiber, dietary calcium (0.83, 0.76-0.90), and potassium. Vitamin D (1.22, 1.01-1.49) and calcium (1.16, 1.00-1.35) supplementation alone increased the risk of stones in meta-analyses of observational studies, but not in RCTs, where the cosupplementation conferred significant risk.

CONCLUSIONS

Several modifiable factors, notably fluid intake, dietary patterns, and obesity, were significantly associated with nephrolithiasis. Long-term RCTs are required to investigate the cost-effectiveness of dietary patterns for stone prevention. The independent and combined effects of vitamin D and calcium supplementation on nephrolithiasis need further elucidation.

Results of the CARDIA study suggest that higher dietary potassium may be kidney protective

The association between dietary sodium and potassium intake with the development of kidney disease remains unclear, particularly among younger individuals. Here, we determined whether dietary sodium and potassium intake are associated with incident chronic kidney disease (CKD) using data from 1,030 adults (age 23-35 in 1990-1991) from the Coronary Artery Risk Development In Young Adults study, based on repeated measurements of estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (ACR) from 1995 through 2015. Urinary sodium and potassium excretion (mg/day), calculated from three 24-hour urine collections in 1990-1991, were averaged to measure sodium and potassium intake. Serum creatinine was used to calculate eGFR using the CKD EPI equation; spot urine albumin and creatinine were used to calculate ACR, each at five visits from 1995-1996 through 2015-2016. CKD was defined as decreased eGFR (under 60 ml/min/1.73m2) or the development of albuminuria (ACR over 30 mg/g). We used log binomial regression models adjusted for socio-demographic, behavioral, and clinical factors to determine whether sodium and potassium intake were associated with incident CKD (decreased eGFR or developed albuminuria) among those free of CKD in 1995. Dietary sodium intake was not significantly associated with incident CKD. However, every 1,000 mg/day increment of potassium intake in 1990 was significantly associated with a 29% lower risk of incident albuminuria (relative risk 0.71, 95% confidence interval 0.53, 0.95), but not eGFR. Thus, higher dietary potassium intake may protect against the development of kidney damage, particularly albuminuria.

Dietary Potassium Intake and Risk of Chronic Kidney Disease Progression in Predialysis Patients with Chronic Kidney Disease: A Systematic Review

The prevalence of chronic kidney disease (CKD) is increasing and dietary interventions may be a strategy to reduce this burden. In the general population, higher potassium intake is considered protective for cardiovascular health. Due to the risk of hyperkalemia in CKD, limiting potassium intake is often recommended. However, given that poor cardiovascular function can cause kidney damage, following a low-potassium diet may be deleterious for patients with CKD. The aim of this systematic review was to summarize the evidence on dietary potassium intake and CKD progression. Multiple databases were searched on 7 June 2019 and data were managed with Covidence. No intervention trials met the inclusion criteria. Eleven observational studies met the inclusion criteria (10 post hoc analyses, 1 retrospective cohort), representing 49,573 stage 1-5 predialysis patients with CKD from 41 different countries. Of the 11 studies, 6 studies reported exclusively on early CKD (stage 1-2), 4 studies separately reported analyses on both early and late (stage 3-5) CKD, and 2 studies reported exclusively on late CKD. A total of 9 studies reported risk of disease progression in early CKD; in 4 studies high potassium intake was associated with lower risk, while in 2 studies the low intake showed a higher progression of risk, and 3 studies reported no relation. In late CKD, results are mixed: 2 studies suggested benefit of higher potassium intake and 1 suggested benefit of lower potassium intake, whereas 3 studies were neutral. These results should be interpreted with caution, as considerations preventing firm conclusions include 1) the overall low range of dietary potassium intake, with all studies reporting an average intake below the 2004 Kidney Disease Outcomes Quality Initiatives guidelines, and 2) the method used to assess potassium intake in most studies (i.e., urine) in late stages of CKD. Ideally, well-controlled intervention studies are needed to understand how dietary potassium intake is linked to CKD progression.

Increasing potassium intake to prevent kidney damage: a new population strategy?

Reducing dietary sodium consumption and increasing potassium intake are effective approaches in reducing the prevalence of cardiovascular diseases. Whether this is also true for chronic kidney disease (CKD) is still debated. Elfassy et al. have examined associations between urinary sodium and potassium excretion and the incidence of CKD in young, 30-year-old subjects followed for 20 years. Although they failed to find an association between sodium intake and CKD incidence, there was an inverse association between high potassium intake and the development of albuminuria.

Dietary sodium, potassium, and blood pressure in normotensive pregnant women: the National Health and Nutrition Examination Survey

Dietary sodium, potassium, and sodium-to-potassium ratio are linearly associated with blood pressure in nonpregnant adults. Earlier investigations suggested null or inverse associations of blood pressure and sodium during normotensive pregnancy; findings have not been confirmed in race/ethnically diverse women or while accounting for potassium. Our purpose was to evaluate associations of blood pressure with sodium and potassium and sodium-to-potassium ratio in race/ethnically diverse normotensive pregnant women. We used cross-sectional blood pressure and dietary data from 984 women in multiple cycles of the National Health and Nutrition Examination Survey (mean age = 27.6 ± 0.2 years). We tested for differences in blood pressure across quartiles of sodium intake using Kruskal-Wallis tests and linear regression to evaluate associations of sodium, potassium, and the sodium-to-potassium ratio with systolic (SBP) and diastolic (DBP) blood pressures. We adjusted for potential confounding variables: age, race/ethnicity, education, marital status, body mass index, smoking, and month of pregnancy. SBP and DBP were similar across quartiles of sodium intake: quartile 1 (lowest sodium intake): 107/59; quartile 2: 106/59; quartile 3: 108/60; quartile 4 (highest sodium intake): 108/58 mm Hg, p > 0.60 for all. Sodium (β = 0.16, 95% confidence interval (CI): -0.20 to 0.52) and potassium (β = 0.18, 95% CI: -0.24 to 0.60) and the sodium-to-potassium ratio (β = -0.54, 95% CI: -1.55 to 0.47) were not associated with SBP or DBP. Results were similar in stratified analyses. Novelty Blood pressure was similar among quartiles of sodium or potassium intake, even in analyses stratified by race/ethnicity and trimester of pregnancy. There was no association of sodium or potassium with blood pressure. Blood pressure may be insensitive to dietary sodium and potassium during normotensive pregnancy.

Food Sources of Potassium in the Average Polish Diet

The aim of this study was to identify the food sources of potassium in the average Polish diet based on the data from the 2016 Household Budget Survey conducted on the representative sample of the Polish population (36,886 households, n = 99,230). This survey is organized by the Central Statistical Office and is related to the expenditures, quantitative consumption and revenues in households. We analyzed 91 sub-groups (i.e., milk, red meat) from 13 food categories (i.e., milk and dairy products, meat and products). Our findings indicated that the daily supply of potassium in the average Polish diet was 2617.9 mg, which meant covering the average allowance in 83%. Vegetables provided 32.5% of potassium, of which potatoes accounted for 16.2% of supply, and other vegetables for 16.2%. Tomatoes as well as other vegetables and mushrooms provided a total of 8.2% of potassium among vegetables. The next position was taken by the meat and meat products category (17.7%), with the largest share of meat products (6.7%) and red meat (5.2%). Cereal products supplied 16.64% of potassium, of which bread, rolls and bread products (12.2%) were of the greatest importance. Milk and dairy products turned out to be the fourth product category as a source of potassium (11.9%), with the highest share of milk (6.8%) and yoghurts and milk drinks (3.9%).

Management of hyperkalemia in patients with kidney disease: a position paper endorsed by the Italian Society of Nephrology

Hyperkalemia (HK) is the most common electrolyte disturbance observed in patients with kidney disease, particularly in those in whom diabetes and heart failure are present or are on treatment with renin-angiotensin-aldosterone system inhibitors (RAASIs). HK is recognised as a major risk of potentially life threatening cardiac arrhythmic complications. When an acute reduction of renal function manifests, both in patients with chronic kidney disease (CKD) and in those with previously normal renal function, HK is the main indication for the execution of urgent medical treatment and the recourse to extracorporeal replacement therapies. In patients with end-stage renal disease, the presence of HK not responsive to medical therapy is an indication at the beginning of chronic renal replacement therapy. HK can also be associated indirectly with the progression of CKD, because the finding of high potassium values leads to withdrawal of treatment with RAASIs, which constitute the first choice nephro-protective treatment. It is therefore essential to identify patients at risk of developing HK, and to implement therapeutic interventions aimed at preventing and treating this dangerous complication of kidney disease. Current strategies aimed at the prevention and treatment of HK are still unsatisfactory, as evidenced by the relatively high prevalence of HK also in patients under stable nephrology care, and even in the ideal setting of randomized clinical trials where optimal treatment and monitoring are mandatory. This position paper will review the main therapeutic interventions to be implemented for the prevention, detection and treatment of HK in patients with CKD on conservative care, in those on dialysis, in patients in whom renal disease is associated with diabetes, heart failure, resistant hypertension and who are on treatment with RAASIs, and finally in those presenting with severe acute HK.

Transcriptomic analysis of the Malpighian tubules of Trichoplusia ni: Clues to mechanisms for switching from ion secretion to ion reabsorption in the distal ileac plexus

Excretion of metabolic wastes and toxins in insect Malpighian tubules (MTs) is coupled to secretion of ions and fluid. Larval lepidopterans demonstrate a complex and regionalized MT morphology, and recent studies of larvae of the cabbage looper, Trichoplusia ni, have revealed several unusual aspects of ion transport in the MTs. Firstly, cations are reabsorbed via secondary cells (SCs) in T. ni, whereas in most insects SCs secrete ions. Secondly, SCs are coupled to neighbouring principal cells (PCs) via gap junctions to enable such ion reabsorption. Thirdly, PCs in the SC-containing distal ileac plexus (DIP) region of the tubule reverse from cation secretion to reabsorption in response to dietary ion loading. Lastly, antidiuresis is observed in response to a kinin neuropeptide, which targets both PCs and SCs, whereas in most insects kinins are diuretics that act exclusively via SCs. Recent studies have generated a basic model of ion transport in the DIP of the larval T. ni. RNAseq was used to elucidate previously uncharacterised aspects of ion transport and endocrine regulation in the DIP, with the aim of painting a composite picture of ion transport and identifying putative regulatory mechanisms of ion transport reversal in this tissue. Results indicated an overall expression of 9103 transcripts in the DIP, 993 and 382 of which were differentially expressed in the DIP of larvae fed high-K⁺ and high-Na⁺ diets respectively. Differentially expressed transcripts include ion-motive ATPases, ion channels and co-transporters, aquaporins, nutrient and xenobiotic transporters, cell adhesion and junction components, and endocrine receptors. Notably, several transcripts for voltage-gated ion channels and cell volume regulation-associated products were detected in the DIP and differentially expressed in larvae fed ion-rich diet. The study provides insights into the transport of solutes (sugars, amino acids, xenobiotics, phosphate and inorganic ions) by the DIP of lepidopterans. Our data suggest that this region of the MT in lepidopterans (as previously reported) transports cations, fluid, and xenobiotics/toxic metals. Besides this, the DIP expresses genes coding for the machinery involved in Na⁺- and H⁺-dependent reabsorption of solutes, chloride transport, and base recovery. Additionally, many of the transcripts expressed by the DIP a capacity of this region to respond to, process, and sometimes produce, neuropeptides, steroid hormones and neurotransmitters. Lastly, the DIP appears to possess an arsenal of septate junction components, differential expression of which may indicate junctional restructuring in the DIP of ion-loaded larvae.

Dietary Practice among the Patients with End Stage Renal Disease undergoing Maintenance Haemodialysis

Introduction

Several studies on the nutritional status of chronic kidney disease patients living on haemodialysis revealed high prevalence of malnutrition (18–94%). A hospital-based study in Nepal revealed 66.7% mild to moderately malnourished and National Kidney Center reported common protein-energy malnutrition problem among haemodialysis patients. As almost all patients undergoing maintenance haemodialysis looked malnourished, this study was carried out to explore prevailing dietary knowledge and practice of the patients.

Methods

A descriptive cross-sectional survey of 471 patients undergoing haemodialysis from June 2015 to July in 2015 was carried out. After stratification through a systematic random sampling method, 40 (67%) patients from National Kidney Center and 20 (33%) from Bir Hospital were selected, interviewed face to face by using structured questionnaire. Ethical and institutional approval and patients' consent were obtained.

Results

The level of knowledge score found to be medium and practice score was even low. Seventy percent knew about renal diet but only 36 (60%) believed in it. After having kidney disease 42 (70%) had changed their dietary practice. Surprisingly, 38 (63.3%) said they ate the food what the other member in their family ate.

Conclusions

Considerable limited knowledge (medium) and practices (low) scores were found. Had they have taken adequate dietician's support, they might have taken right kind and right amounts of foods and benefitted in controlling potassium, phosphate and protein at the recommended level. Plant-based diet could assist in end stage renal disease in a number of ways: an edge of protection against diet cost, reduce inter-related co-morbidities or complications (hypertension and diabetes).

Invited Commentary: Can Estimation of Sodium Intake Be Improved by Borrowing Information From Other Variables?

Estimation of dietary sodium intake is problematic. The most accurate measure is average sodium excretion from multiple 24-hour urine collections, but such an approach is impractical. Using data from the Women's Health Initiative, Prentice et al. (Am J Epidemiol. 2017;186(9):1035-1043) assessed the relationship of calibrated estimates of sodium and potassium excretion with cardiovascular outcomes. The calibrated estimates were a function of self-reported sodium-to-potassium ratio from a food frequency questionnaire, age, body mass index, race, supplement use, smoking status, educational level, income, and aspirin use. In general, associations with outcomes using the calibrated estimates were in the expected direction: direct for the sodium-to-potassium ratio and sodium intake and indirect for potassium. The unexpected associations were an increased risk of hemorrhagic stroke with lower sodium-to-potassium ratio and sodium intake and increased risk with higher potassium intake, along with a null relationship of sodium intake with ischemic stroke. Overall, our assessment is that the authors have improved the estimation of mean dietary sodium and potassium intakes. However, more work is needed to show that calibrated estimates actually improve estimation of future clinical events. If this methodological issue can be successfully addressed, their approach has the potential to improve estimation of dietary sodium and potassium intakes in observational studies.

Urinary Sodium-to-Potassium Ratio Tracks the Changes in Salt Intake during an Experimental Feeding Study Using Standardized Low-Salt and High-Salt Meals among Healthy Japanese Volunteers

The Na/K ratio is considered to be a useful index, the monitoring of which allows an effective Na reduction and K increase, because practical methods (self-monitoring devices and reliable individual estimates from spot urine) are available for assessing these levels in individuals. An intervention trial for lowering the Na/K ratio has demonstrated that a reduction of the Na/K ratio mainly involved Na reduction, with only a small change in K. The present study aimed to clarify the relationship between dietary Na intake and the urinary Na/K molar ratio, using standardized low- and high-salt diets, with an equal dietary K intake, to determine the corresponding Na/K ratio. Fourteen healthy young adult volunteers ingested low-salt (3 g salt per day) and high-salt (20 g salt per day) meals for seven days each. Using a portable urinary Na/K meter, participants measured their spot urine at each voiding, and 24-h urine was collected on the last day of each diet period. On the last day of the unrestricted, low-salt, and high-salt diet periods, the group averages of the 24-h urine Na/K ratio were 4.2, 1.0, and 6.9, while the group averages of the daily mean spot urine Na/K ratio were 4.2, 1.1, and 6.6, respectively. The urinary Na/K ratio tracked changes in dietary salt intake, and reached a plateau approximately three days after each change in diet. Frequent monitoring of the spot urine Na/K ratio may help individuals adhere to an appropriate dietary Na intake.

Evaluation of the 24-Hour Recall as a Reference Instrument for Calibrating Other Self-Report Instruments in Nutritional Cohort Studies: Evidence From the Validation Studies Pooling Project

Calibrating dietary self-report instruments is recommended as a way to adjust for measurement error when estimating diet-disease associations. Because biomarkers available for calibration are limited, most investigators use self-reports (e.g., 24-hour recalls (24HRs)) as the reference instrument. We evaluated the performance of 24HRs as reference instruments for calibrating food frequency questionnaires (FFQs), using data from the Validation Studies Pooling Project, comprising 5 large validation studies using recovery biomarkers. Using 24HRs as reference instruments, we estimated attenuation factors, correlations with truth, and calibration equations for FFQ-reported intakes of energy and for protein, potassium, and sodium and their densities, and we compared them with values derived using biomarkers. Based on 24HRs, FFQ attenuation factors were substantially overestimated for energy and sodium intakes, less for protein and potassium, and minimally for nutrient densities. FFQ correlations with truth, based on 24HRs, were substantially overestimated for all dietary components. Calibration equations did not capture dependencies on body mass index. We also compared predicted bias in estimated relative risks adjusted using 24HRs as reference instruments with bias when making no adjustment. In disease models with energy and 1 or more nutrient intakes, predicted bias in estimated nutrient relative risks was reduced on average, but bias in the energy risk coefficient was unchanged.

Cardiovascular benefits associated with higher dietary K+ vs. lower dietary Na+: evidence from population and mechanistic studies

The World Health Organization ranks hypertension the leading global risk factor for disease, specifically, cardiovascular disease. Blood pressure (BP) is higher in Westernized populations consuming Na⁺-rich processed foods than in isolated societies consuming K⁺-rich natural foods. Evidence suggests that lowering dietary Na⁺ is particularly beneficial in hypertensive individuals who consume a high-Na⁺ diet. Nonetheless, numerous population studies demonstrate a relationship between higher dietary K⁺, estimated from urinary excretion or dietary recall, and lower BP, regardless of Na⁺ intake. Interventional studies with K⁺ supplementation suggest that it provides a direct benefit; K⁺ may also be a marker for other beneficial components of a "natural" diet. Recent studies in rodent models indicate mechanisms for the K⁺ benefit: the distal tubule Na⁺-Cl^- cotransporter (NCC) controls Na⁺ delivery downstream to the collecting duct, where Na⁺ reabsorbed by epithelial Na⁺ channels drives K⁺ secretion and excretion through K⁺ channels in the same region. High dietary K⁺ provokes a decrease in NCC activity to drive more K⁺ secretion (and Na⁺ excretion, analogous to the actions of a thiazide diuretic) whether Na⁺ intake is high or low; low dietary K⁺ provokes an increase in NCC activity and Na⁺ retention, also independent of dietary Na⁺ Together, the findings suggest that public health efforts directed toward increasing consumption of K⁺-rich natural foods would reduce BP and, thus, cardiovascular and kidney disease.

A case of extreme hypokalaemia

Hypokalaemia is a common clinical problem. It can lead to severe disturbances in cardiac, neurological and muscle function. We present the case of a 45-year-old woman who was transported to our hospital with cardiac arrest following ventricular fibrillation. Blood sampling revealed severe acidosis (pH 7.02) and extreme hypokalaemia (0.9 mmol/l). The low serum potassium level was most likely caused by the combination of a very deficient diet and use of a thiazide diuretic. She never reported any symptoms. An acute intracellular shift of potassium due to epinephrine and perhaps also the cathecholamines in Red Bull may have further decreased the serum potassium concentration. To our knowledge, this is the lowest potassium level reported in literature. Longer-lasting hypokalaemia might be asymptomatic but when combined with even minor triggers of acute hypokalaemia, serious morbidity or mortality can suddenly occur. Patients on diuretic treatment with suspected malnutrition or chronic gastrointestinal losses require regular monitoring of electrolytes.

Dietary Protein and Potassium, Diet-Dependent Net Acid Load, and Risk of Incident Kidney Stones

BACKGROUND AND OBJECTIVES

Protein and potassium intake and the resulting diet-dependent net acid load may affect kidney stone formation. It is not known whether protein type or net acid load is associated with risk of kidney stones.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We prospectively examined intakes of protein (dairy, nondairy animal, and vegetable), potassium, and animal protein-to-potassium ratio (an estimate of net acid load) and risk of incident kidney stones in the Health Professionals Follow-Up Study (n=42,919), the Nurses' Health Study I (n=60,128), and the Nurses' Health Study II (n=90,629). Multivariable models were adjusted for age, body mass index, diet, and other factors. We also analyzed cross-sectional associations with 24-hour urine (n=6129).

RESULTS

During 3,108,264 person-years of follow-up, there were 6308 incident kidney stones. Dairy protein was associated with lower risk in the Nurses' Health Study II (hazard ratio for highest versus lowest quintile, 0.84; 95% confidence interval, 0.73 to 0.96; P value for trend <0.01). The hazard ratios for nondairy animal protein were 1.15 (95% confidence interval, 0.97 to 1.36; P value for trend =0.04) in the Health Professionals Follow-Up Study and 1.20 (95% confidence interval, 0.99 to 1.46; P value for trend =0.06) in the Nurses' Health Study I. Potassium intake was associated with lower risk in all three cohorts (hazard ratios from 0.44 [95% confidence interval, 0.36 to 0.53] to 0.67 [95% confidence interval, 0.57 to 0.78]; P values for trend <0.001). Animal protein-to-potassium ratio was associated with higher risk (P value for trend =0.004), even after adjustment for animal protein and potassium. Higher dietary potassium was associated with higher urine citrate, pH, and volume (P values for trend <0.002).

CONCLUSIONS

Kidney stone risk may vary by protein type. Diets high in potassium or with a relative abundance of potassium compared with animal protein could represent a means of stone prevention.

Nutrient Non-equivalence: Does Restricting High-Potassium Plant Foods Help to Prevent Hyperkalemia in Hemodialysis Patients?

Hemodialysis patients are often advised to limit their intake of high-potassium foods to help manage hyperkalemia. However, the benefits of this practice are entirely theoretical and not supported by rigorous randomized controlled trials. The hypothesis that potassium restriction is useful is based on the assumption that different sources of dietary potassium are therapeutically equivalent. In fact, animal and plant sources of potassium may differ in their potential to contribute to hyperkalemia. In this commentary, we summarize the historical research basis for limiting high-potassium foods. Ultimately, we conclude that this approach is not evidence-based and may actually present harm to patients. However, given the uncertainty arising from the paucity of conclusive data, we agree that until the appropriate intervention studies are conducted, practitioners should continue to advise restriction of high-potassium foods.